This application claims the benefit of Korean Patent Application No. 2001-62359, filed Oct. 10, 2001, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a fusing apparatus of an electrophotographic image forming apparatus, and more particularly, to a fusing apparatus having an internal pipe maintaining a surface temperature of a fusing roller at a uniform level without a temperature deviation.
2. Description of the Related Art
FIG. 1 is a schematic perspective view of a conventional electrophotographic image forming apparatus. Referring to FIG. 1, the conventional electrophotographic image forming apparatus includes a paper ejecting unit 1, an operating unit 2, a control board cover 3, an upper cover opening button 4, a paper display window 5, a multi-purpose feeding window 6, a paper cassette 7, an option cassette 8, and an auxiliary stand 9.
FIG. 2 is a schematic cross-sectional view of a conventional fusing apparatus 10 of the conventional electrophotographic image forming apparatus employing a halogen lamp as a heat source. Referring to FIG. 2, the conventional fusing apparatus 10 includes a cylindrical fusing roller 11 and a heat-generating portion 12, e.g., the halogen lamp, installed at an interior center of the fusing roller 11.
A coating layer 11a, such as Teflon, is coated on a surface of the fusing roller 11. The heating-generating portion 12 generates heat inside the fusing roller 11, and the fusing roller 11 is heated from an interior surface thereof by a radiant heat transmitted from the heat-generating portion 12.
FIG. 3 is a longitudinal sectional view illustrating a relationship between the fusing apparatus 10 and a pressure roller 13 of the conventional electrophotographic image forming apparatus employing the halogen lamp as the heat source as shown in FIG. 2.
Referring to FIG. 3, the pressure roller 13 is disposed to face a paper 14 in a lower portion of the fusing apparatus 10. The pressure roller 13 is elastically supported by a spring device 13a to press the paper 14 toward the fusing roller 11 with a predetermined pressure, and the paper 14 passes between the fusing roller 11 and the pressure roller 13. A powdered toner image 14a is formed on the paper 14 and is pressed with the predetermined pressure and heated by heat while passing between the fusing roller 11 and the pressure roller 13. In other words, the toner image 14a is fixed onto the paper 14 by the heat of the fusing roller 11 and the pressure of the pressure roller 13.
A thermistor 15 measuring the surface temperature of the fusing roller 11 and a thermostat 16 cutting off the supply of power when the surface temperature of the fusing roller 11 exceeds a predetermined set value, are provided at one side of the fusing apparatus 10. The thermistor 15 measures the surface temperature of the fusing roller 11 and transmits an electric signal corresponding to the measured temperature to a controller (not shown) of a printer (not shown). The controller controls an amount of electricity supplied to the halogen lamp 12 according to the measured temperature to maintain the surface temperature of the fusing roller 11 within a given range. When the temperature of the fusing roller 11 exceeds the predetermined set value because the thermistor 15 and the controller fails in controlling the temperature of the fusing roller 11, a contact (not shown) of the thermostat 16 becomes open to cut off the supply of power to the halogen lamp 12.
Such a conventional fusing apparatus using the halogen lamp as the heat source unnecessarily consumes a large amount of electric power. Particularly, when power is turned on, the conventional fusing apparatus requires quite a long warming-up time. In other words, until the fusing roller 11 reaches a desired temperature after applying power, a predetermined time must elapse. The warming-up time may range from several tens of seconds to several minutes. In addition, in the conventional fusing apparatus, since the fusing roller 11 is heated by radiation transmitted from the heat source, heat transmission is slow, and compensation for a temperature deviation caused by a decrease in temperature occurring due to a contact with the paper 14 is slow, so it is difficult to maintain the temperature of the fusing roller 11 constant. Moreover, since the electric power must be periodically applied to the heat source in order to maintain the temperature of the fusing roller 11 constant in a standby mode in which an operation of the printer is in pause, unnecessary electric power is consumed. A considerable time is required to convert the standby mode into an operation mode for an image output, and thus it is difficult to achieve a fast image output.
FIG. 4 is a schematic longitudinal sectional view of another conventional fusing apparatus employed in the electrophotographic image forming apparatus. Referring to FIG. 4, a heating plate 22 is provided at an inner bottom portion of a flexible, cylindrical film tube 21. A pressure roller 23 having a spring device 23a is disposed to face the heating plate 22 at a lower portion thereof and the paper 14 is disposed therebetween.
The film tube 21 is rotated by a separate rotating device. Although it consumes a lower power to locally heat a portion between the heating plate 22 and the pressure roller 23, it is difficult to achieve fast printing in the fusing apparatus of FIG. 4.
In order to solve the above problem, fusing apparatuses adopting a heat pipe capable of instantaneously heating the fusing roller using a high heat conductivity and having a low power consumption characteristic are disclosed in Japanese Patent Publication Nos. JP6348176, Hei 11-282294, and Hei 2000-25976.
The fusing apparatuses adopting the heat pipe are configured such that different heat sources are arranged at one portion of the fusing roller, the one portion deviating from a fusion area. Such arrangement of the heat sources may result in an increase in an overall size of the fusing apparatus, which needs to be improved in an increased structural complexity.
The fusing apparatuses disclosed in Japanese Patent Publication Nos. Showa 60-55368, Hei 4-335691, Hei 4-360185, Hei 8-171301, Hei 8-262905, Hei 8-305195 and 9-90811, may not have the increased structural complexity due to the heat source incorporated into the fusing roller. However, since these apparatuses have a plurality of the heat pipes locally disposed in the fusing roller, a manufacturing process is very complex. Also, since the heat pipes are locally disposed in the fusing roller, there is a temperature difference between a space between two adjacent heat pipes and portions directly contacting the heat pipes. Thus, since there is a difference in the surface temperature throughout a heat pipe, the toner image cannot be fixed properly on the paper, and a print quality of the toner image fixed on the paper deteriorates.
To solve the above and other problems, it is an object of the present invention to provide a fusing apparatus having an internal pipe with improved fusibility by maintaining an entire surface temperature of a fusing roller at a uniform level without a temperature deviation.
Additional objects and advantageous of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
To achieve the above and other objects of the invention, there is provided a fusing apparatus of an electrophotographic image forming apparatus. The fusing apparatus includes an internal pipe having a tubular body portion and end portions integrally formed with the body portion at both ends of the body portion, a heat-generating portion installed to wrap the body portion to be in close contact with the body portion without a gap and to generate heat, and a fusing roller installed so as to wrap the heat-generating portion.